1. Field of the Invention
The present invention generally relates to an underwater pelletizer in which a molten polymer is extruded through die orifices in a die plate in the form of continuous strands that are cut into pellets by a rotatable knife assembly having sharp edges engaged with a die face which includes the discharge ends of the die orifices. More specifically, the invention relates to an underwater pelletizer of simple but yet efficient and dependable construction in which the rotatable blade assembly associated with the die face is driven from a standard foot mounted electric motor having a standard C-flange attachment in which the pelletizer shaft is keyed to the motor shaft and held in place by a set screw with the key being welded in a slot in the pelletizer shaft to facilitate its manufacture. The pelletizer shaft includes a spring loaded cutter hub enabling automatic blade adjustment and compensating for misalignment with the spring loaded cutter hub being keyed to the pelletizer shaft by a key that is welded in a slot in the spring loaded cutter hub to simplify its manufacture and provide a positive and dependable drive connection to enable movement of the portion of the spring loaded cutter hub connected with the blade assembly. The die plate is provided with carbide tiles and the blade assembly includes tungsten carbide blades to provide extended die wear and extended blade wear. The pelletizer shaft includes a slinger to prevent any liquid migrating through the shaft seal from running along the shaft and getting into the motor bearings. A weep hole is provided in the adaptor connected to the motor flange to dischage seal leakage and a secondary weep slot is provided on the adaptor at its junction with the motor flange to provide additional assurance that liquids leaking past the seal and slinger will not migrate into the motor bearings.
2. Description of the Prior Art
Underwater pelletizers have been used for a number of years to form pellets or granuals of plastic material and various patents have been granted relating to various improved pelletizer structures including U.S. Pat. Nos. 4,123,207; 4,251,198; 4,500,271; 4,621,996; and 4,728,276 owned by the Assignee of this invention. Additionally, prior patents exist which disclose a spring loaded type of hub structure interconnecting a drive shaft and a cutter blade assembly as illustrated in the following patents.
U.S. Pat. No. 3,196,487 PA0 U.S. Pat. No. 3,266,090 PA0 U.S. Pat. No. 4,422,372 PA0 U.S. Pat. No. 4,421,470 PA0 U.S. Pat. No. 4,874,307
While many developments and improvements have been made in underwater pelletizers, the above mentioned patents do not disclose the specific structural arrangements disclosed in this application.